Journal of Arid Environments 74 (2010) 1413e1417 Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv Territory size of the Mourning Wheatear Oenanthe lugens along an aridity gradient F. Khoury a,*, N. Boulad b a Department of Biological Sciences and Biotechnology, The Hashemite University, P.O. Box 150459, Zarqa 13115, Jordan b Research and Survey Section, Royal Society for the Conservation of Nature, P.O.Box 1215, Jubeiha 11941, Amman, Jordan article info abstract Article history: Breeding territories of Mourning Wheatear Oenanthe lugens were investigated in three study areas in Received 15 September 2009 Jordan to describe and explain variation in territory size along an aridity gradient. In moderately Received in revised form productive semi-deserts, Mourning Wheatears defended small territories (averages for two different 22 January 2010 areas 3.0 ha and 5.9 ha) that were arranged as relatively dense neighbourhood clusters, while in Accepted 11 May 2010 extremely arid deserts, territories were significantly larger (average 22.8 ha) and arranged in very loose Available online 9 June 2010 clusters. Contender pressure and probably vegetation cover (as cue of sustained prey availability) played a dual role in determining territory sizes. The relative role of prey availability as proximate factor Keywords: Contender pressure increased with aridity due to low contender pressure in extremely arid deserts. Ó Desert 2010 Elsevier Ltd. All rights reserved. Jordan Productivity Territoriality 1. Introduction Wheatears, genus Oenanthe, are insectivorous birds that aggressively defend exclusive, food-related breeding territories Territory size in animals often relates inversely to food abun- against both conspecific intruders and heterospecific competitors dance (food-value theory), i.e. territories tend to be smaller when of their same genus; most Oenanthe species inhabit arid regions resources are more available (Adams, 2001; Hixon, 1980; Myers between central Asia and North Africa, the Middle East forming the et al., 1979; Stenger, 1958). For the proximate mechanisms that centre of their distribution (Cornwallis, 1975; Panov, 2005). Terri- cause this pattern, three hypotheses have been proposed (e.g. Pons torial birds inhabiting arid environments face the difficulty of et al., 2008): according to the first hypothesis, an animal assesses ensuring that the areas they defend provide adequate food. To prey density directly and accordingly adjusts territory size to secure their energy needs, such birds are expected to adjust the include resources sufficient for its energetic needs, while the characteristics of their territories, mainly territory size. We studied second hypothesis postulates that an animal uses cues, usually the relationship of the size of Mourning Wheatear (Oenanthe a structure within the habitat that correlates with prey density. The lugens) breeding territories to various factors, including total third hypothesis assumes that territory size is constrained by vegetation cover (as indicator of food abundance) and competitor intraspecific competition, i.e. when food is more abundant, more abundance in arid regions in Jordan. Different populations inhab- competitors will be attracted, making the area more costly to iting habitats with variable aridity were compared during the defend, hence the smaller territory sizes. While a number of studies breeding season. We predicted that prey density or another reliable support the third or “contender pressure hypothesis” (Dunk and cue of resource availability (vegetation cover) will affect territory Cooper, 1994; Myers et al., 1979; Pons et al., 2008), others provide size in arid environments with limited food resources. differing results, i.e. territory sizes were determined directly by prey density (McFarland, 1986; Temeles, 1987) or indirectly by 2. Methods and material a habitat cue that correlates with prey abundance (Smith and Shugart, 1987). Most of these studies were carried out in 2.1. Study species and areas temperate or tropical bioclimates, whereas very few studies were conducted in arid regions where resources are extremely limited. The Mourning Wheatear (O. lugens lugens) is a small insectivo- rous passerine bird (body mass: 22e28 g) that is fairly widespread in Jordan in arid areas that nevertheless vary in rainfall and produc- * Corresponding author. Tel.: þ962 6 5683494. tivity (Fig. 1). This distribution granted us the opportunity to carry E-mail addresses: [email protected], [email protected] (F. Khoury). out spatial and inter-population comparisons across environmental 0140-1963/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2010.05.010 1414 F. Khoury, N. Boulad / Journal of Arid Environments 74 (2010) 1413e1417 Fig. 1. Distribution of Mourning Wheatear Oenanthe lugens in Jordan. The black morph breeds only in the basalt desert (Al-Harra) of north-east Jordan (after Andrews, 1994, modified). gradients in arid ecosystems. The Mourning Wheatear is a typical dominated by dwarf shrubs e.g. Ballota undulata, Noaea mucro- bird of the rift margins of western Jordan, where it inhabits stonyand nata and Artemisia herba-alba in addition to the desert broom rocky slopes and steep-sided wadis in arid and sparsely-vegetated Retama raetam. Grazing pressure is high during winter and spring hilly or mountainous areas. It is also found locally on low limestone when the study site is used as rangeland for goats and sheep by escarpments and wadis in the eastern desert of Jordan (Andrews, semi-nomadic Bedouins and locals from a nearby village. 1995). Birds of the rare black morph are restricted to the undu- b. The arid mountains of Dlagha and Jebel Mas’uda, south of Petra lating basalt desert landscape of north-east Jordan where they (approx. 30120 N, 35270 E; altitude 990e1600 m a.s.l.), where inhabit areas with wadis, road cuttings and boulder piles (Andrews, the mean annual precipitation is in the range of 120e200 mm. 1994). Two territories belonging to black morph birds were also Precipitation falls in this area as rain and snow mainly during the included in this study. The subspecies lugens occurs in the Middle cool winter season and early spring (NovembereMarch). The East, including Jordan (Cramp,1988; Panov, 2005; Shirihai, 1996). In vegetation on the stony and rocky mountain slopes is sparse, this subspecies, there is no obvious sexual dimorphism (Panov, dominated by dwarf shrubs, e.g. A. herba-alba, N. mucronata or 2005). Although considered a resident bird (Andrews, 1995), the Anabasis articulata. Grazing pressure is high, and most of the Mourning Wheatear is not strictly sedentary: in Jordan, most indi- area is densely populated during the winter by nomadic viduals carry out seasonal movements, some apparently moving to Bedouins who own large sheep herds. slightly higher areas in JuneeAugust, i.e. after the breeding season, c. The eastern desert of Jordan, where two sites with mean annual and many usually moving to lower areas for the winter. Breeding precipitation below 90 mm were studied. Rain falls in this area in territories are usually occupied by March and the breeding season the cool winter months and occasionally also in spring (Novem- extends up to June. bereMay). The first, al-Dahek (31340 N, 37090 E, altitude: Field observations on territory size were carried out in three 500e550 m a.s.l.), is a limestone escarpment where a small regions (Fig. 1.) with obvious variation in rainfall (National Atlas of population of 5e10 pairs of Mourning Wheatear exists. The Jordan, 1984) and vegetation (Albert et al., 2004): wheatears held territories along barren limestone slopes and cliffs that border to an open flood plain, holding a dry salt marsh a. The north-west-facing slopes above Wadi al-Wala/al-Heydan with a moderate cover of low Tamarix sp. shrubs. The second area (approx. 31300 N, 35430 E; altitude 415e625 m a.s.l.), where the was located in the undulating basalt desert (Harra desert) near mean annual precipitation is around 250 mm, falling mainly Safawi (3210 N, 37300 E). Vegetation is scarce in the black basalt during the cool winter season and early spring (Novem- desert and dominated by dwarf shrubs (e.g. Astragalus spinosum, bereMarch). Vegetation cover is moderate, dominated by various Achillea fragrantissima) that are usually confined to small dwarf shrubs, and with a relatively rich annual cover during depressions and wadi beds. Grazing pressure by sheep herds is spring. The vegetation is generally a mosaic of Mediterranean- rather high along the wadis. Most of the Mourning Wheatears type (semi-steppe batha) and Irano-Turanian Artemisia steppe, recorded in the basalt desert are of the black morph. 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